The long-term goal of this research project is to study relationships between exposure to fumonisins and microcystins and human liver and esophageal cancer risks in high-risk populations. Fumonisins and microcystins are newly identified environmental biotoxins that are produced by toxicogenic fungi and cyanobacteria, respectively. Fumonisins are carcinogens and both fumonisins and microcystins are strong tumor promoters in animal models. Human populations in certain areas of world are exposed to higher levels of these toxins in their daily life mainly through contaminated dietary components and/or drinking water. Both of these toxins have been etiologically linked to high incidence of human primary liver cancer and esophageal cancer in several areas of South Africa and China. Although analytical methods for detecting these toxins in environmental samples have been reported and potential biomarkers, such as disruption of sphingolipids metabolism by fumonisins and inhibition of protein phosphatases by microcystins, have been found in animal models, validation of these biomarkers in humans, especially in high-risk populations, has not been done or reported. To date, methods are still lack for simultaneously detection of these toxins in environmental samples and human body fluids, which are critical for assessment of human cancer risks, because co-exposure to these biotoxins in high-risk populations has been widely reported. In this exploratory research project, we will develop and validate analytical array methods to simultaneously measure these biotoxins in both environmental samples and human body fluids. We will use molecular epidemiological tools to validate methods for biomarkers in body fluids of cases of primary liver cancer and esophageal cancer and controls. The working hypothesis underlying this research proposal is that long-term exposure to fumonisins and microcystins may induce synergistic carcinogenic effects in high-risk individuals and application of validated biomarkers can improve the quantitative estimation of human cancer risk from exposure to these biotoxins. The specific aims are: 1) to develop rapid and sensitive analytical array method(s) for measuring fumonisin and microcystin biomarkers based on previously developed immunoaffinity-HPLC method for aflatoxins and/or HPLC-enzyme-linked immunosorbent assay for microcystins; 2) to validate method(s) for measuring biomarkers of microcystins and fumonisins in food, water, and body fluids such as blood and urine samples collected from two one-week longitudinal biomonitoring studies in human subjects from high-risk areas of primary liver cancer and esophageal cancer, and 3) to perform molecular epidemiological studies in two high-risk populations of primary liver cancer and esophageal cancer in Qidong and Huaian, P.R. China, for exploring cancer risks from exposures to fumonisins and microcystins.